1. Field of the Invention
The present invention generally relates to a disk apparatus and control methods therefor, and more particularly to a disk apparatus in which recording and retrieving of data are performed with heads that follows tracks on a disk and a control method therefor.
2. Description of the Related Art
In magnetic disk drives, such as hard disk drives, concentric tracks are formed on a disk. A head follows the track and writes or reads information on the track. The head also reads servo information recorded at predetermined positions on the tracks. A head position is detected and, then, the head is controlled to follow the desired track.
In hard disk drives, disks are usually fixed to a spindle motor first and, after that, servo information is written to the disks. Therefore, a center of disk rotation coincides with a center of the concentric tracks. However, because of disk variation with temperature and time, the center of disk rotation may no longer coincide with the center of the concentric tracks. This causes so-called eccentricity.
It is a general object of the present invention to provide a disk apparatus and a control method therefore in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a disk apparatus and a control method therefore which achieves exact tracking error correction control against disk eccentricity.
The above objects of the present invention are achieved by a method for controlling a disk apparatus in which heads scan tracks on a disk to record or retrieve information. The method includes a position error detection procedure which detects a position error between the head and the track, a phase control procedure which advances a phase of the position error detected by the position error detection procedure by a predetermined value and a head control procedure which controls a position of the head according to the position error which is advanced in phase by the phase control procedure.
The above objects of the present invention are also achieved by an apparatus in which heads scan tracks on a disk to record or retrieve information. The disk apparatus includes a position error detection unit which detects a position error between the head and the track, a phase control unit which advances a phase of the position error detected by the position error detection unit by a predetermined value and a head control unit which controls a position of the head according to the position error which is advanced in phase by the phase control unit.
According to this invention, the phase of the detected position error is advanced by the predetermined value. Then, the heads are controlled according to the phase-advanced position error. Consequently, a delay of head control is compensated for so that tracking is performed exactly.
According to this invention, a position error is detected for each frequency and the phase of the detected position error is advanced by a predetermined value for each frequency. Then, the phase-advanced position errors are synthesized and the heads are controlled by the synthesized position error. Consequently, the tracking is performed exactly because it is possible to lead phase for each frequency.
Further, according to this invention, because the detection of position errors and leading phase of the position errors can be performed in order for each frequency, it is possible that a load of processing is reduced.